Motor-sparing effect of iPACK (interspace between the popliteal artery and capsule of the posterior knee) block versus tibial nerve block after total knee arthroplasty: a randomized controlled trial

Abstract

Background and objectiveAn ultrasound-guided anesthetic technique targeting the interspace between the popliteal artery and capsule of the posterior knee (iPACK) can provide posterior knee analgesia with preserved motor function after total knee arthroplasty (TKA). This study compared the peroneal nerve motor-sparing effects of iPACK block and tibial nerve block (TNB) when combined with local infiltration analgesia (LIA) and continuous adductor canal block (CACB).MethodsIn this study, 105 patients scheduled for elective TKA were randomized to receive proximal iPACK block (iPACK1), distal iPACK block (iPACK2), or TNB, along with spinal anesthesia, modified LIA, and CACB. The primary outcome was the incidence of common peroneal nerve (CPN) motor blockade. Secondary outcomes included CPN sensory function, tibial sensorimotor function, posterior knee pain, pain score, intravenous morphine requirement, timed up-and-go test, quadriceps muscle strength, range of motion, length of hospital stay, patient satisfaction, and adverse events.ResultsThe incidence of CPN motor blockade was significantly higher in the TNB group than in the iPACK1 (p=0.001) and iPACK2 (p=0.001) groups, but was not significant between the iPACK1 and iPACK2 groups (p=0.76). Tibial nerve motor function was more preserved in the iPACK1 and iPACK2 groups than in the TNB group (p<0.001 and p<0.001, respectively). Complete CPN and tibial sensorimotor blockade were not observed in the iPACK2 group. Posterior knee pain score was significantly higher in the iPACK1 group than in other groups during the 24-hour postoperative period (p=0.001).ConclusionsCompared with TNB, iPACK1 and iPACK2 preserved CPN and tibial nerve motor function to a greater extent. However, iPACK2 did not demonstrate complete CPN and tibial nerve motor blockade while maintaining effective posterior knee pain relief.Trial registration numberTCTR20180206002.

Ultrasound-Guided Local Anesthetic Infiltration Between the Popliteal Artery and the Capsule of the Posterior Knee (IPACK) Block for Primary Total Knee Arthroplasty: A Systematic Review of Randomized Controlled Trials

“…The search strategy identified 2180 unique citations. After independent and duplicate screening by two authors (RSD and BL), eight RCTs 13,[25][26][27][28][29][30][31] were identified that fulfilled eligibility criteria. Collectively, these eight RCTs consisted of 777 patients (377 patients received the iPACK block; 400 patients in the control cohort received another modality of peripheral nerve blockade or PAI for knee analgesia).…”

“…All eight RCTs 13,[25][26][27][28][29][30][31] generally demonstrated a low risk of bias in random sequence generation and allocation concealment, blinding of outcome assessment, incomplete outcome data, and selective reporting. In terms of blinding of participants, some RCTs 13,25,26 displayed a high risk for bias because although they blinded all surgeons, recovery room and floor nurses, research assistants, statisticians, and patients, it was impossible to blind the anesthesiologist performing the ultrasound-guided iPACK block who may have participated in the study. Furthermore in one study, 13 operating room nurses provided the local anesthetic medication to the anesthesiologist based on the type of regional block and thus were also not blinded.…”

“…Other sources of bias included no true control group without a posterior knee block, and unequal dose of local anesthetic between study arms. For the primary anesthetic, five studies 13,25,28,29,31 administered neuraxial anesthesia, two studies 26,27 either administered general anesthesia or neuraxial anesthesia per the discretion of the primary anesthesia team, and one study administered general anesthesia only. 30 All RCTs excluded patients who had a history of chronic pain or utilized preoperative opioids.…”

“…30 All RCTs excluded patients who had a history of chronic pain or utilized preoperative opioids. 13,[25][26][27][28][29][30][31] Local and Regional Anesthesia 2021:14 https://doi.org/10.2147/LRA.S303827…”

“…Local anesthetic dosing regimen for iPACK blocks varied widely with three different types of local anesthetic medications utilized in included studies (ropivacaine, bupivacaine, and levobupivacaine). Five studies 25,26,[29][30][31] included epinephrine in the local anesthetic solution for the iPACK block. The most common formulation for iPACK was 0.25% levobupivacaine with epinephrine.…”